It has previously been proposed to prepare encapsulates of volatile liquids such as volatile natural or synthetic flavouring oils and perfumes in various carrier materials such as starch and dextrin derivatives by spray-drying emulsions containing the carrier material and volatile liquids (see, for example, U.S. Pat. No. 3,159,585).
However, in any spray-drying equipment, the particle size of the product from the spray-drying tower is thought to be related to the possible residence time of the droplets in the tower and of the ability of the particles to agglomerate and if large particles are required, a large tower must be used, which will inherently mean the production of large quantities of encapsulate material. In addition the viscosity characteristics of some carrier materials in emulsion or solution form can cause problems in atomisation in spray-drying towers.
Attempts have been made to obtain larger particles by the agglomeration of spray-dried particles in an agglomerator. However, when using a pan granulator or fluidised bed agglomeration to increase the size of spray-dried particles containing a volatile liquid, significant losses of that liquid are found to occur either during the agglomeration process or in subsequent storage, probably as a result of changes in the particle structure and their effect on its retention of the volatile liquid.
For various uses in the flavour and perfumery field, relatively small quantities of very specialised encapsulates are required and it is desirable that these encapsulates are of a particle size greater than that which can be achieved using small pilot plant spray-drying towers.
For example, it is desirable to introduce into fabric detergent washing powders encapsulates containing perfumes and it is difficult, using normal, small spray-drying equipment, to produce such encapsulate particles greater than 100 microns diameter. Ideally, for use in a fabric detergent powder, an encapsulate would be of the order of 500 microns diameter and such particles cannot be produced except in very large spray-drying towers of the size used in producing the detergent powder itself.
Similar criteria are involved in producing flavour-containing encapsulate particles for use in the foods industry and the present invention provides a process for the production of encapsulates of substantially greater size than those which can be made in small spray-drying towers which do not generate powder flow problems and which can readily be re-dissolved in, for example, water, without lumping or clustering together and so slowing down their solution.